The embodiments described herein relate generally to gas turbine engines, and more specifically to methods and systems for operating gas turbine engines.
Known gas turbine engines generally include a compressor, one or more combustors that each include a fuel injection system, and a turbine section. In at least some known engines, the combustors are typically arranged in an annular array about the engine and are interconnected for the purposes of ignition. The compressor raises the pressure of inlet air, and then channels the pressurized air towards the combustors, where it cools the combustion chamber walls and is used in the combustion process. More specifically, in the combustion chamber, compressed air is mixed with a fuel and the mixture is ignited to produce hot combustion gases.
In some known combustion turbines, the turbine may be powered using either a fuel gas or a liquid fuel. Such turbines may have fuel supply systems for both liquid and gas fuels, but generally do not burn both gas and liquid fuels simultaneously. Rather, when the combustion turbine burns liquid fuel, the gas fuel supply may be removed from service. Alternatively, when the combustion turbine burns fuel gas, the liquid fuel supply may be removed from service.
In some known industrial combustion turbines, the combustion system may include an array of combustors that each includes at least one liquid fuel nozzle and at least one gas fuel nozzle. In such an arrangement, combustion may be initiated within the combustion chamber slightly downstream from the fuel nozzles. Air from the compressor may flow around and through the combustors to provide oxygen for combustion.
Some known gas turbine engines include multiple fuel circuits for each fuel type that may operate during predetermined modes of operation. When one circuit is removed from service, fuel in the idle circuit may remain in the idle fuel manifold. However, hot combustion gases or hot air may flow back from the combustors into the idle fuel circuit and ignite the residual fuel. To prevent this occurrence, known gas turbine engines may purge the idle manifold with either compressor discharge air or inert gas such as nitrogen to remove the residual fuel from the manifold. However, known purge systems are expensive and complicated to operate.
Accordingly, there exists a need for a simplified and cost effective fuel system that prevents the flow of hot combustion gases between the combustors and the idle fuel circuit.